A general framework for photoionization calculations applied to nonthermal gas discharges in air

2020

JGR Space Physics

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A framework is developed to model photoionization of metals deposited in the lower ionosphere as a result of meteoric ablation and photodetachment of electrons from negative ions of the Earth's ionosphere due to sources of emission other than solar radiation. A wide range of the electromagnetic spectrum including cases of negligible, moderate, and significant absorption of radiation is considered. We limit our scope to the radiation transport through lower ionospheric regions, in case when molecular oxygen, O2, is considered as the main absorber of radiation as photoabsorption due to ozone is only effective at stratospheric altitudes and molecular nitrogen, N2, is transparent to radiation with wavelengths longer than ∼100 nm. We model photon transport in an exponential atmosphere and derive efficient differential representations of the problem in case of negligible photoabsorption and constant pressure approximations. Photoabsorption asymmetry in the atmosphere is demonstrated in case of photons with absorption scales comparable to the scale height of the atmosphere. The application of the model to photoionization in the lower ionosphere is demonstrated by considering photoionization of meteoric species due to photons of the Lyman‐Birge‐Hopfield (LBH) band system of N2 observed in the aurora and in the lightning‐induced transient luminous events. Furthermore, we model detachment of electrons from negative ions of the ionosphere due to the first positive and the second positive band systems of N2, and the first negative band system of N 2+, also observed in the sources mentioned above.

“…The rate of photoionization (i.e., number of photoionization events per unit volume per unit time) per unit density of a species located at position

\overset{r}{true}

due to a source comprised of volumetric elements dV ′ located at

\overset{r}{true}'

is given by (e.g., Janalizadeh & Pasko, 2019, and references therein):

{scriptR}^{{pi}_{normal1}} false(\overset{r}{true} false) = \int_{λ} \int_{V^{'}} ε false(\overset{r}{true}', λ false) normalexp false[- τ^{pa} false(\overset{r}{true}, \overset{r}{true}', λ false) false] \frac{σ^{pi} false(λ false)}{4 π R^{2}} d V^{'} d λ,

where

\overset{R}{true} = \overset{r}{true} - \overset{r}{true}'

and therefore,

R = false| \overset{r}{true} - \overset{r}{true}' false|

(see Figure 2). Note that the superscript 1 in

{scriptR}^{{pi}_{normal1}} false(\overset{r}{true} false)

emphasizes that the photoionization rate is calculated per unit density of the considered species that are being photoionized, and

{scriptR}^{pi} false(\overset{r}{true} false) = n^{pi} false(\overset{r}{true} false) {scriptR}^{{pi}_{normal1}} false(\overset{r}{true} false)

where

n^{pi} false(\overset{r}{true} false)

is the density of the photoionized species.…”

Section: Rate Of Photoionization Scriptrpifalse(truer→false) and Phomentioning

confidence: 99%

Section: Rate Of Photoionization Scriptrpifalse(truer→false) and Phomentioning

confidence: 99%

“…Introducing the source photon emission rate

I false(\overset{r}{true} false)

and denoting the normalized energy distribution function of the emitted photons (i.e., normalized emission spectrum) by s ( λ ) such that

\int_{λ} s false(λ false) d λ = 1

, and therefore

ε false(\overset{r}{true}, λ false) = I false(\overset{r}{true} false) s false(λ false)

(see Janalizadeh & Pasko, 2019), Equation reduces to

{scriptR}^{{pi}_{normal1}} false(\overset{r}{true} false) = \int_{V^{'}} I false(\overset{r}{true}' false) \frac{g^{pi} false(\overset{r}{true}, \overset{r}{true}' false)}{4 π R^{2}} d V^{'}

where

g^{pi} false(\overset{r}{true}, \overset{r}{true}' false) = \int_{λ} s (λ) normalexp false[- τ^{pa} false(\overset{r}{true}, \overset{r}{true}', λ false) false] σ^{pi} false(λ false) d λ

is referred to as the photon propagator of the species being considered and is the factor governing the possibility of photoionization at distance R between source point

\overset{r}{true}'

and observation point

\overset{r}{true}

Section: Rate Of Photoionization Scriptrpifalse(truer→false) and Phomentioning

confidence: 99%

b^{'} {}^{1}{Σ_{u}^{+}}

c_{4}^{'} {}^{1}{Σ_{u}^{+}}

{c_{3}}^{1} Π_{u}

, and

{o_{3}}^{1} Π_{u}

states of N 2 to the ground state

X^{1} Σ_{g}^{+}

, respectively.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Framework for Efficient Calculation of Photoionization and Photodetachment Rates With Application to the Lower Ionosphere

Janalizadeh

2020

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Conditions for Inception of Relativistic Runaway Discharges in Air

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et al. 2023

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Terrestrial gamma ray flashes (TGFs) (Fishman et al., 1994) represent a spectacular naturally occurring high energy phenomenon in the Earth's atmosphere. These events contain photons with several tens of mega electron-volt energies and likely involve large quantities of energetic electrons, sharing the same physical origin as X-rays generated by laboratory sparks (Stankevich & Kalinin, 1967) or originating from stepping lightning leaders (Moore et al., 2001). Dwyer et al. (2012) provide a review of principal physical processes and experimental findings on TGFs and related phenomena.It has been discovered by Dwyer (2003) that in order to explain observed intensities of TGFs a feedback mechanism should be involved in these events when an avalanche of relativistic electrons launches positrons and X-rays backwards at its origin to provide additional seeding and replenishment of the avalanche. Dwyer (2003) noted a physical analogy between this relativistic feedback mechanism and feedback mechanisms in conventional Townsend discharges involving positive ions and optical photons. The self-consistent modeling of a large scale streamer (domain size ∼5 km) and related space charge effects driven by the relativistic feedback discharges in air around 11-12 km altitudes have been reported by Dwyer (2012) and Liu and Dwyer (2013). It has been

Preliminary Modeling of Magnetized Sprite Streamers on Jupiter Following Juno's Observations of Possible Transient Luminous Events

Janalizadeh

2023

JGR Space Physics

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The first observation of possible transient luminous events (TLEs) on Jupiter was recently reported by Giles et al. (2020). This is a finding that resembles the serendipitous capture of Earth's TLEs on camera three decades ago (Franz et al., 1990). Specifically, the ultraviolet spectrograph (UVS) aboard the Juno spacecraft has recorded 11 optical signals during the first 4 years of the mission that may have originated from TLEs on Jupiter. Light curves for 10 of the flashes show a mean decay time of ∼1.4 ms while the remaining flash has a noticeably shorter duration (i.e., 0.1 ms), which possibly may be because Juno's UVS was triggered immediately before the photodetector moved off the flash. Additional properties of the detected flashes and the observation geometry may be found in Giles et al. (2020, Table 1). 2020) use a model of radiative transfer in Jupiter's atmosphere to locate the altitude of flashes. It is concluded that the best fit to the recorded spectrum of flashes is obtained for a source altitude of ∼258 km above the 1-bar level (i.e., ∼10 μbar pressure). Giles et al. ( 2020) emphasize that UV observations cannot probe altitudes below that corresponding to 100 mbar. As such, the UV signature of lightning, which is generally thought to occur at ∼5 bar and even the recently observed "shallow lightning" (Becker et al., 2020) that occurs at pressures higher than 1.4 bar will be absent from Juno UVS observations (e.g., Moses et al., 2005, Figure 8). It is therefore clear that Giles et al. (2020) did not observe typical lightning discharges. Giles et al. (Previous observations of Jupiter lightning were limited by camera sensitivity, distance from Jupiter and long exposures. This contributed to the exclusive detection of Jupiter lightning with optical energies comparable to terrestrial superbolts (e.g., Turman, 1977) (i.e., ∼10 9 J). Juno's observations of Jupiter, however, has led to the conclusion that Jupiter lightning predominantly consists of flashes with optical energies similar to typical terrestrial energies (i.e., 10 5 -10 8 J) (Becker et al., 2020, Figure 2). Kolmašová et al. (2018) report a much higher lightning frequency, which is comparable to the frequency of lightning on Earth, and Becker et al. (2020) report an increase in the flash rate from ∼4 × 10 −3 to ∼6.1 × 10 −2 flashes per square kilometer per year with several flashes